'four applications' - were not all requests for permission.
We were advised (by the council) to regularise (or make lawful) 2 and 3 with LDC's (and have substantially the completed works), before we submit 4.
Application 2 is in case application 3 is refused.
The Pre-App helped us gain finance ... we also had 'pre' pre-app meetings, and the approach is what they advised.
We did our due diligence on the designer, someone well versed and experienced in this particular type of application, and others we are also to make, I have had bad experiences before - but not sure I should go doubting his judgement here.
I agree we could have gone off and simply built the loft and 3mt ground without application, but the 6mt still requires an Application, and party wall is 6/7 weeks before works can begin in earnest, so rather than go against what the council advise - keep them happy and follow the protocol.
I think what you are suggesting is one App for permission goes in, get your PD works up before planning officer arrives to inspect (about 5 weeks after validation) - no need for PD LCD's, a PD LDC would still need to be submitted for the 6mt though ... the 6mt app went in after the 3mt, and only after the scheme was unexpectedly extended.